Shutdown issues

[Ralph Lange <Ralph.Lange@gmx.de>]

All,

Since Michael had to take back some of the epicsExit() changes, I was 
thinking about how to do a smooth transition to a smarter IOC 
shutdown/restart.
This is coming back to a suggestion that Andrew had a few months back:
Do we need a staged shutdown process with hooks for each stage - similar 
to the initHooks mechanism?
At that point there would also be a clearer definition of which stages 
are shut down for a "hot standby" or a "warm complete restart" of the IOC.
Maybe the module could also declare its name and functionalities, e.g. 
as an or'ed mask of features like "supports_standby", 
"supports_restart", "supports_link_change", etc so that the IOC core can 
decide if and how to do restart/shutdown and can provide better diagnostics.
So that instead of simply setting
    epicsAtExit(func, arg);

a module would set things along the line of
    id = epicsExitRegister("myModule", supports_standby|supports_restart);
    epicsAddExitHook(id, EXIT_BEFORE_CORE, func1, arg1);
    epicsAddExitHook(id, EXIT_BEFORE_SERVER, func2, arg2);
    epicsAddExitHook(id, EXIT_BEFORE_DBSCAN, func3, arg3);
    epicsAddExitHook(id, EXIT_BEFORE_ERRLOG, func4, arg4);

Compatibility - epicsAtExit could do
    {
        bla = epicsExitRegister("$$filename$$", 0);
        epicsAddExitHook(bla, EXIT_BEFORE_CORE, func, arg);
    }

What do you think? Too much boilerplate? Functionality missing?

~Ralph